feat: add Tailwind CSS and PostCSS configuration

- Created postcss.config.js to configure PostCSS with Tailwind CSS and Autoprefixer.
- Updated svelte.config.js to enable PostCSS preprocessing.
- Added tailwind.config.js for Tailwind CSS configuration.
- Updated yarn.lock to include new dependencies for Tailwind CSS, PostCSS, and related plugins.

svelte.config.js

@@ -9,6 +9,7 @@ module.exports = {
         sveltePreprocess({
             sourceMap: true,
             typescript: false,
+            postcss: true,
         }),
     ],
 }